mother-out-law

From mother +‎ -out-law, by analogy to mother-in-law.

mother-out-law (plural mothers-out-law)

1. The mother of one's boyfriend or girlfriend.
2. The mother of any of one's friends.
3. The mother of one's ex-spouse.
   • 2006, Harlyn Aizley, Confessions of the Other Mother: Nonbiological Lesbian Moms Tell All!‎ (Social Science), →ISBN, pZgDAQAAQBAJ, page 36:

     The old Cape Cod commune-istas had caught up enough with my mother out-law and were now asking after notable events in the lives of her offspring.

• mother-in-law

• brother-out-law
• daughter-out-law
• father-out-law
• sister-out-law
• son-out-law